This gene locus controls recovery from viremia and leukemia induced by Friend virus (FV). This recessive allele is found in BALB/c, and A.BY strains and is associated with high FV titers after inoculation. This allele produces an alternative mRNA transcript that excludes exon 2 and produces a protein that is 3- to 5- fold less potent in anti-viral activity as the protein encoded by the Apobec3Rfv3-s allele.